WHATEVER HAPPENED TO...?

The Newest Generation Gap: Carrying a Handkerchief

Jean Bradley writes: ''I was always bothered by the drop of moisture that appeared on President Nixon's top lip. It made me wish he would wipe it away. And during the O.J. trial, I observed Mr. Cochran repeatedly wipe his nose with his fingers. Is he too poor (in manners) to know about the discreet use of a handkerchief?''

Roman senators used them to dab sweat from their brows. Medieval knights carried them as the vaunted symbol of a lady's favor. Today, handkerchiefs remain popular with older folks, but the younger set seems to prefer tissues.

For Judith Martin - also known as Miss Manners - the fashion of handkerchiefs will never fade, however. And, as usual, her defense has a practical edge: ''I'm puzzled,'' she says, ''as to why handkerchiefs have gone out of style, when sneezing hasn't.'' Furthermore, ''It does make you a little alarmed to shake hands with someone who doesn't have one.''

Handkerchiefs have social utility, too. ''It was a great flirtation device: A lady would drop her handkerchief, a gentleman would pick it up, they would immediately fall in love'' - a good scenario for Miss Manners, whose newest book is ''Miss Manners on Painfully Proper Weddings.''

Also, it was ''a gentlemanly gesture,'' she says, for a man to offer a weeping woman a handkerchief, ''though it was usually he who made the lady cry.''

For those in need who want the real thing - for their nose or social life - Barneys in New York has top-notch white cotton versions with blue or tan borders for $15. At J.C. Penney, 13 permapress cotton hankies are just $10.

''Until the human being is redesigned,'' Miss Manners says, ''there will always be a need for handkerchiefs.''